We have a 2020 Ram 1500 Limited running 35" tyres. Used the Rough Country calibrator which updates the tyre size in the BCM. We then had to also update the radio/sat nav as that didn't pickup the new tyre size straight away and the navigation goes haywire. It seems that it still uses the wheel speed pulses to calculate speed and distance travelled. After forcing the Radio to update, all is good EXCEPT the PTS (parking sensors etc.) Will not work as the PTS module reports "Vehicle Line Mismatch" and switches itself off as it doesn't like the new tyre size.
If you set the tyre size back to factory it works again, as soon as you set 34.5 (which seems the accurate rolling diameter for a 35") it refuses to operate. So we have a choice of speed under-reading by 6% and the sat-nav going haywire but having park sensors that work, or having the correct speed and no front or rear park sensors.
Dealers cannot change tyre size with wiTECH on 2020 model year vehicles, - FCA have removed the option. Even before this, dealers could only select tyres that were originally available from the factory. We have been told it is to do with the vehicles being certified by EPA with the specific tyres fitted by the factory and no EPA certification existing for any other size.
But people are going to change their tyres anyway irrespective of emissions certification.
Not being possible to correctly adjust the BCM / TCM and PTS to reflect this change is dangerous. The vehicle will either be travelling at greater speeds than indicated, or its built in safety features (Parksense) will not function properly. This is hardly ideal. It would be far safer to allow the vehicle systems to be updated to show the correct tyre size.
Has anyone had similar issues with tire size and PTS and managed to find a work around? Any help appreciated!
